1. Technical Field
The present technical field relates to a wound-type electrolytic capacitor and a method for manufacturing the same.
2. Background Art
Recently, as electronic apparatuses have higher performance, capacitors to be mounted on the electronic apparatuses is required to have larger capacitance and smaller equivalent series resistance (ESR). As such capacitors, a wound-type solid electrolytic capacitor is widely used. The solid electrolytic capacitor includes a capacitor element, a bottomed cylindrical exterior case housing the capacitor element, and a sealing member for sealing an opening part of the exterior case. The capacitor element includes a wound body. The wound body includes a positive electrode foil, a negative electrode foil, and a separator. On a surface of the positive electrode foil, a dielectric film is formed. In the wound body, the positive electrode foil and the negative electrode foil are wound in a state where the negative electrode foil is laminated on the positive electrode foil. The separator is laminated with the positive electrode foil and the negative electrode foil in such a manner in which the separator is interposed between the positive electrode foil and the negative electrode foil. The wound body is impregnated with a conductive polymer. The conductive polymer forms a solid electrolyte layer.
In a manufacturing process of the above-mentioned solid electrolytic capacitor, the wound body is impregnated with the conductive polymer by using polymerization methods such as an electrolytic polymerization method and a chemical polymerization method. Specifically, firstly, the wound body is immersed in a polymerization solution for forming the conductive polymer. Thus, the polymerization solution permeates a gap existing inside the wound body through the separator. Then, the conductive polymer is generated inside the wound body by polymerizing monomers in the polymerization solution. However, such a method makes a manufacturing process of a solid electrolytic capacitor complicated.
Then, as a method for impregnating a wound body with a conductive polymer, the following technique has been proposed. Firstly, a wound body is impregnated with a dispersion of a conductive polymer or a solution of a conductive polymer. Thus, the dispersion or the solution permeates a gap existing inside the wound body through a separator. Thereafter, the dispersion or the solution with which the wound body is impregnated is dried. As a result, the conductive polymer remains inside the wound body, and the conductive polymer forms a solid electrolyte layer.